/**
 * 接口1:
 * distanceSort(target, num1,num2 ,...)
 * 根据各个 num 在数轴上距 target 远近来排序
 * @param target : number  目标，参考数
 * @param num : number    参与比较的数
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 *
 *
 * 接口2:
 * distanceSort(target, nums)
 * 根据 nums 各个数在数轴上距 target 远近来排序
 * @param target : number  目标，参考数
 * @param nums : [number]    参考比较的数的数组
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 */
Math.distanceSort = function distanceSort(target, ...nums) {
  let numList = nums;

  let firstNum = nums[0];
  if ( (nums.length == 1) && Array.isArray(firstNum)) {
    numList = firstNum.slice();
  }

  let disSort = numList.sort(function (a,b) {
    return Math.abs(a - target) - Math.abs(b - target) ;
  });

  return disSort;
}






/**
 * 接口1:
 * nearest(target, num1,num2 ,...)
 * 返回距 target 最近的数
 * @param target : number  目标，参考数
 * @param num : number    参与比较的数
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 *
 *
 * 接口2:
 * nearest(target, nums)
 * 返回距 target 最近的数
 * @param target : number  目标，参考数
 * @param nums : [number]    参考比较的数的数组
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 */
Math.nearest = function nearest(target, ...nums) {
  let disSort = Math.distanceSort(target,...nums);
  return disSort[0];
}




/**
 * 接口1:
 * farthest(target, num1,num2 ,...)
 * 返回距 target 最远的数
 * @param target : number  目标，参考数
 * @param num : number    参与比较的数
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 *
 *
 * 接口2:
 * farthest(target, nums)
 * 返回距 target 最远的数
 * @param target : number  目标，参考数
 * @param nums : [number]    参考比较的数的数组
 * @returns [number]   返回 按距离 target 从近到远排列的数的数组
 */
Math.farthest = function farthest(target, ...nums) {
  let disSort = Math.distanceSort(target,...nums);
  let lastIndex = disSort.length - 1;
  return disSort[lastIndex];
}












window.accAdd = function(num1, num2) {
  num1 = Number(num1);
  num2 = Number(num2);
  var dec1, dec2, times;
  try { dec1 = countDecimals(num1)+1; } catch (e) { dec1 = 0; }
  try { dec2 = countDecimals(num2)+1; } catch (e) { dec2 = 0; }
  times = Math.pow(10, Math.max(dec1, dec2));
  // var result = (num1 * times + num2 * times) / times;
  var result = (accMul(num1, times) + accMul(num2, times)) / times;
  return getCorrectResult("add", num1, num2, result);
  // return result;
};

window.accSub = function(num1, num2) {
  num1 = Number(num1);
  num2 = Number(num2);
  var dec1, dec2, times;
  try { dec1 = countDecimals(num1)+1; } catch (e) { dec1 = 0; }
  try { dec2 = countDecimals(num2)+1; } catch (e) { dec2 = 0; }
  times = Math.pow(10, Math.max(dec1, dec2));
  // var result = Number(((num1 * times - num2 * times) / times);
  var result = Number((accMul(num1, times) - accMul(num2, times)) / times);
  return getCorrectResult("sub", num1, num2, result);
  // return result;
};

window.accDiv = function(num1, num2) {
  num1 = Number(num1);
  num2 = Number(num2);
  var t1 = 0, t2 = 0, dec1, dec2;
  try { t1 = countDecimals(num1); } catch (e) { }
  try { t2 = countDecimals(num2); } catch (e) { }
  dec1 = convertToInt(num1);
  dec2 = convertToInt(num2);
  var result = accMul((dec1 / dec2), Math.pow(10, t2 - t1));
  return getCorrectResult("div", num1, num2, result);
  // return result;
};

window.accMul = function(num1, num2) {
  num1 = Number(num1);
  num2 = Number(num2);
  var times = 0, s1 = num1.toString(), s2 = num2.toString();
  try { times += countDecimals(s1); } catch (e) { }
  try { times += countDecimals(s2); } catch (e) { }
  var result = convertToInt(s1) * convertToInt(s2) / Math.pow(10, times);
  return getCorrectResult("mul", num1, num2, result);
  // return result;
};

var countDecimals = function(num) {
  var len = 0;
  try {
      num = Number(num);
      var str = num.toString().toUpperCase();
      if (str.split('E').length === 2) { // scientific notation
          var isDecimal = false;
          if (str.split('.').length === 2) {
              str = str.split('.')[1];
              if (parseInt(str.split('E')[0]) !== 0) {
                  isDecimal = true;
              }
          }
          let x = str.split('E');
          if (isDecimal) {
              len = x[0].length;
          }
          len -= parseInt(x[1]);
      } else if (str.split('.').length === 2) { // decimal
          if (parseInt(str.split('.')[1]) !== 0) {
              len = str.split('.')[1].length;
          }
      }
  } catch(e) {
      throw e;
  } finally {
      if (isNaN(len) || len < 0) {
          len = 0;
      }
      return len;
  }
};

var convertToInt = function(num) {
  num = Number(num);
  var newNum = num;
  var times = countDecimals(num);
  var temp_num = num.toString().toUpperCase();
  if (temp_num.split('E').length === 2) {
      newNum = Math.round(num * Math.pow(10, times));
  } else {
      newNum = Number(temp_num.replace(".", ""));
  }
  return newNum;
};

var getCorrectResult = function(type, num1, num2, result) {
  var temp_result = 0;
  switch (type) {
      case "add":
          temp_result = num1 + num2;
          break;
      case "sub":
          temp_result = num1 - num2;
          break;
      case "div":
          temp_result = num1 / num2;
          break;
      case "mul":
          temp_result = num1 * num2;
          break;
  }
  if (Math.abs(result - temp_result) > 1) {
      return temp_result;
  }
  return result;
};
